The present invention relates to piston pumps for very viscous materials. More particularly, it relates to a distributor for such pumps.
In the rubber manufacturing industry, when it is desired to pass unvulcanized rubber continuously through a die in order to obtain a given shape or sheet of rubber, a screw extruder is generally employed. The rotation of the screw makes it possible to transfer the unvulcanized rubber continuously from an inlet trap through which it is generally introduced in the form of a slab or else in the form of a thick strip towards the head of the extruder, where it is compressed under a certain pressure. The rubber then passes through an extrusion orifice of suitable shape.
This technique does not permit complete control of the volumes extruded. For this reason, the prior art also includes a pump for raw rubber described in U.S. Pat. No. 5,261,795. This pump employs a piston which slides within a cylinder. The introduction is effected through ports arranged in the cylinder at a point close to the bottom dead center of the stroke of the piston. The discharge of the rubber from the cylinder is effected through an orifice having a flap valve. The proper operation of such a volumetric pump depends, in particular, on perfect control of the movements of the valve. This leads to preference for a positively actuated valve rather than a simple ball which is held against its seat by a back pressure.